5.2 Public key certificate for RSA scheme

In its turn , the entity requiring an EMV ¢ public key certificate also runs an RSA scheme, regardless of whether it is used for digitally signing information (see Appendix D, Section D.3) or for creating a digital envelope that encrypts a PIN using the asymmetric encryption mechanism (see Appendix D, Sections D.1.2 and D.5.5).

Correspondingly, the parameters entity public key modulus and entity public key exponent submitted for certification correspond to the modulus n and the public exponent e , respectively, of an RSA scheme. For this reason the Public Key Algorithm Indicator ”which is an item in the certificate specifying the type of algorithm that uses the certified parameters ”is set at the moment to a unique value 01h corresponding to the RSA algorithm.

The entity private signing key, which is denoted ( n _S , d _S ) in the RSA context, can be used for generating a digital signature on a message. Everyone having the corresponding entity public verification key, which is denoted ( n _S , e _S ) in the RSA context, and (part of) the message that is signed can verify the correctness of the signature.

The entity can use the entity private decryption key, which is denoted ( n _E , d _E ) in the RSA context, to decrypt any digital envelope computed with the corresponding entity public encryption key, which is denoted ( n _E , e _E )in the RSA context.

Note that when the storage space of the entity allows it, an entity keeps separate key pairs (private key/public key) for signing and encrypting [i.e., (( n _S , d _S )/( n _S , e _S )) and (( n _E , d _E )/( n _E , e _E )), respectively].